Electrical condenser



Dec. 12, 1950 P. R. COURSEY ELECTRICAL CONDENSER 4 Sheets-Sheet 1 FiledFeb. 28, 1947 WV w n m TN m 4 A W W lx mm P 4 Sheets-Sheet 3 Filed Feb.28, 1947 FIG/2.

Inventor A llorncv Patented Dec. 12, 1950 ELECTRICAL CONDENQER PhilipRay Coursey, Liss, England, assignor to Engineering DevelopmentLaboratories, Inc., New York, N \Y., a corporation of New YorkApplication February 28', 1947, Serial No. 731,507 In Great BritainDecember 6, 1946 9 Claims. (01. 175- -41) This invention relates toelectrical condensers of the kind in which the electrodes and insulatingspacers are const tuted by interleaved fiexible elements of sheetmaterial spirally wound about a central axis, so that the convolutionsof the electrode elements, such for example as metal foil, are separatedby the convolutions of the flexible spacer elements, such for example aspaper or other fibrous or porous material, the rolled unit being usuallytreated with a suitable impregnant.

According to the specification of the United States of America patentapplication Serial No. 718,634, dated December 2'7, 1946, the flexibleelements are wound on a single central core held in tension while beingrotated about the longitudinal axis of the core which is preferablyconstituted by a wire driven at both ends simultaneously. It has,hitherto, been found desirable for somepurposes to enclose a smallcondenser of the rolled type within a cash: of moud ble material, suchfor example as Bakelite. The condenser is usually wound, impregnated andthe terminal leads attached, this unit being finally enclosed, by meansof a moulding press, within the said casing. With this method, however,it is difiicult to obtain moisture-proof seals where the terminal leadsleave the casing, so that moisture may find access to the rolledcondenser within the casing. Moreover, the heat applied during themoulding operation is liable to affect themsulation and electricalqualities of the condenser unit, and one object of the present inventionis to overcome these difiiculties. A further object of the invention isto provide improvements in or modifications of the core upon which theinterleaved flexible elements are spirally wound. These and furtherobjects will become apparent from the appended claims and the followingdescription of the accompanying drawings, in which Figure 1 is adiagrammatic representation, in side elevation, of apparatus forspirally winding the interleaved flexible elements,

Figure 2 illustrates in vertical section on the line II-II of Figure 1,the chucks and winding gear only,

Figures 3 to 6 show on an enlarged scale the steps involved in anchoringthe ends of the fiexible strips relatively to the core,

Figure 7 shows the rolled unit in side elevation,

Figure 8 illustrates the condenser unit of Figure '7 arranged within aceramic tube which is Figure 11 is a view similar to that of Figure 6but for a rolled unit employing a conducting core,

Figure 12 illustrates one arrangement of a condenser un t according toFigure 11 arranged with:v

in a moulded casing shown in longitudinal section,

Figures 13 and 14 are similar views of yet a further arrangement, Figure13 showing the meta1 pot in section whilst Figure 14 shows the pot inelevation,

Figures 15 to 17 show three modified arrangements respectively, and

Figure 18 indicates a modified arrangement of a twin core which may beemployed.

As shown in Figures 1 and 2, two plastc mono film or similar threads Ahaving an overall diameter of approximately 0.0012 to 0.0015 of an inchare threaded through the axial bores in two aligned rotary chucks B resectively, carried between sunports A1 mounted on a base A2, one or eachof the chucks having an'axial micrometer adjustment B1 (Figure 2)whereby the threads A can be subjected to a requ red degree ofmechanical tension after the core A has been gripped in the chucks B bytightening the he ds B2. The two chucks B are driven, in synchronism,through a handle Ba and tooth gearing B4, so that the drive is appliedto both ends of the core A simul-, taneously. Carried by members C, D onthe base A2 with their axes parallel to the axs of rotation of the coreA are a pluralityof supply rolls two of which C1, C2 are const tuted bystrips of metal foil whilst the two others D1, D2 are constituted bystrips of paper which are to constitute the insulating spacers betweenthe foils or electrodes. The foils C1, C2 have a thickness of, say, notmore than five microns (0.0002 inch approximately) whilst the spacersD1, D may have a thickness of up to 12 microns (0.0005 inch approximatly) if used singly or up to 6.5 to 7.0 microns (0.00025 to 0.0003 inchapproximately) if used in pairs. Where single paper spacers are used itis sometimes found advantageous to coat one or both sides of them, butpreferably one side only, with a layer of lacquer or varn sh for thepurpose of filling up the irregularities in the paper surface which isad acent to a metal electrode and so to reduce the liabilities tobreakdown through this portion of the tissue,

As shown in Figure 3 the free end of the paper strip D1 is insertedbetween the insulating threads A of the core extending between thechucks B so that when the core is rotated by means of the handle B; thepaper strip D1 will be wound on the core which then acts as a mandreluntil the strip 3 D1 laps the core as shown. The end or the foil 01 istaken over two guide rollers E1 interconnected by an inclined ramp E andthence to the angle formed between the core A and the first paper stripD1 tangential thereto. The handle B: is now turned slightly so that theend or the foil C1 is wound in, whereupon the end or the second paperstrip D2 is laid over the foil C1 and thence to the angle between thestrip C1 and the first convolution of the strip D1, as shown in Figure4. Having .again turned the handle B: through a small angle to wind inthe end or the paper strip Dz, the end of the second foil C: is laidover a guide roller D4 and inserted into the angle between the secondpaper strip D1 and the adjacent convolution of the first paper strip D1.The handle B3 is now turned until the several foils and paper strips arewound as shown in Figure 6, the foils C1 and C1 and the second paperstrip D1 being cut so that the strip D2 extends beyond the ends or thefoils. The winding is now completed until the first paper strip D1 lapsthe roll whereupon the paper strip D1 is severed and has its end securedby adhesive as shown at C; (Figure 7) The foils are so wound relativelyto the paper spacers that whilst one edge C4 of the foil C1 lies whollywithin the confines oi! the paper strips D1, Dz the other edge C5 of thefoil C1 projects beyond the confines oi the said paper strips. Similarlyone edge Co of the foil C2 lies wholly within the confines of the paperstrips D1, D1 whilst the other edge C1 of the foil C11 projects beyondthe paper strips. Thus the two metal foils 01,01 have their marginaledges C5, C1 projecting so as to constitute terminal connections for thepurpose described below. It will be understood that thedistances'between the ends of the paper convolutions and the adjacentedges C4, Cs of the foils are considerably exaggerated for the sake ofclarity of illustration, only narrow margins being actually required inpractice. Having cut off the two pro- 'jecting ends of the core A, therolled unit shown in Figure 7 is inserted in a ceramic tube G (Figure 8)having internal metallised areas G1 so that when terminal leads F, F1are soldered to the opposite terminal connections C5, C1, these aresimultaneously soldered to the metallised areas G1. These solderedconnections are such that they provide moisture-proof seals at the endsof the ceramic tube G whose contents, that is to say the rolledcondenser elements, are thus sealed against the entry of moisture.

It will be understood that though in the arrangements above describedthe core is constituted by two insulating threads, the core may beconstituted by a single insulating thread, such for example as asynthetic resin, the first flexible element being then merely attachedto the core by adhesive. Moreover, since the core is of insulatingmaterial and is not employed as one or the condenser terminals, eitherone of the flexible spacer elements, or one of the foils, may beconnteicted to the core for initiating the winding opera on.

The rolled unit shown in Figures 7 and 8 may be treated with animpregnant of mineral wax, oil, jelly or the like, or with an impregnantof high dielectric constant, such for example as one of the chlorinatednaphthalenes or chlorinated diphenyls or a wax-like hydrogenated orhydroxylated castor oil, impregnation being effected before the terminalleads F, F1 are soldered to the terminal connections so as to seal theconvolutions of the rolled unit.

When two or more threads are included in the core, for example thethreads A in Figures 1 to 6, the threads may be or circularcross-section as shown at A4 in Figure 18, or in the form or fiat stripsor other cross-sectional shapes (e. g. of D-'- section when twin threadsare employed as in Figures l to 6), which will fit together to form therequisite cross-sectional profile for the core.

In Figure 9 the rolled unit is'as described with reference to Figure 7except that the interleaved flexible foils and paper strips are wound ona single core A; of insulating material, the first paper strip D1 beingsecured to the core A: by means of adhesive whereupon the unit is woundas described with reference to Figures 3 to 6 above. Having severed thetwo ends of the core A: level with the projecting ends C5, C1 of thefoils C1, C2, two terminal end plates F1, F1 soldered (or otherwiseattached e. g. by riveting or In the modification shown in Figure 10 theends I of the ceramic tube G are'closed bymetallised ceramic plugs J, J1which are soldered to the metallised ends G1 of the ceramic tube G, theterminal leads K, K1 extending from the terminal connections C1,Crthrough apertures in the plugs J, J1 with the leads K, K1 soldered tothe plugs J, J1 around said apertures, the terminal leads K, K1 beingsoldered to the connections C1, C5 through metal discs m, K1. Thoughthis condenser may be employed without a surrounding insulating housing,Figure 10 shows the sealed unit moulded within a casing H1, for exampleoi. Bakelite or other mouldable material.

It will be apparent that instead or the tube G being of ceramicmaterial, it may be of metal into which the ceramic plugs J, J1 aresoldered. Alternatively, whether the tube G is of ceramic material or ofmetal, only one ceramic plug may be used, the other terminal beingconnected to the metal tube by insertion of a solid disc of metal toclose one end of it. The unit rolled upon an insulating core may, ifdesired, be disposed and sealed within a metal sleeve or thimble, thesealing being effected by an insulating washer or bush such for exampleas a ceramic plug through which the terminal lead extends. The sealedunit may then be moulded within a casing of mouldable insulatingmaterial such for example as Bakelite.

Figure 11 shows a construction in which the flexible foils and paperstrips are wound on a central metallic core or wire L which is heldunder tension between the chucks B in the manner described above. Withthis arrangement a first metallic foil M is soldered to the core L asdescribed in the copending application referred to above, the first andsecond foils M, M1 and the spacing paper strips N, N1 being woundsuccessively as described. The second foil M1 laps the outercircumierence of the rolled unit and a terminal tag 0 wound into theunit is connected as shown in Figure 12 to a tinned metal sleeve orcylinder 01 which is open at both ends. Inserted into one end of thecylinder 01 is a metallised ceramic plug P1 through which one end of theconducting core or wire L extends, the other end or said core being cutoil flush with the adjacent end of the rolled unit. The plug P1 iscircumferentially soldered to the tinned metal cylinder 01 whilst thepartof the plug P1 embracing the core L is similarly soldered thereto.The ceramic plug Pi thus seals the corresponding end of the cylinder 01.An insulating washer P2, for example of mica, is inserted into the otherend of the cylinder 01 whereupon a metal disc Pa electrically andmechanically connected to at'erminal lead L1 is inserted over the washerP2 and this terminal lead soldered to the cylinder 01 and tag 0. Thus,one end of the core or mandrel L constitutes one terminal lead whilstthe other terminal lead L1 is connected to the metallic cylinder whoseinterior is sealed at both ends against access of moisture. Beforesealing, the rolled unit is treated with an impregnant as indicatedabove. The impregnated and sealed condenser with its axially projectingterminal leads L, L1 is now moulded in a Bakelite or similar plastichousing.

P thus forming an insulating moulded unit with the terminal leads L, Liextending from the housing or casing P.

It will be apparent that with constructions in which the sealed unit ismoulded within an insulating housing, the' paper strips and foils of thecondenser will be protected, not only against mechanical and electricaldamage by direct contact with the mouldable material, but also againstthe direct action of the moulding heat whilst,

' since the rolled unit itself will be moisture-proof,

access-of moisture to the spirally wound elements will be prevented evenshould the joints where the leads emerge from the moulded casing not bewholly moisture-proof.

In the arrangement shown in Figures 13 and 14 the condenser unit rolledon a metal core L as described with reference to Figure 12 is arrangedin a pot-like terminal thimble Q of tinned metal and having along.tudinal slit Q1 whose edges are electrically connected to theexposed portion of the outer metal foil M1 by applying a soldering ironthereto. Arranged in the base of the thimble Q is an insulating disc Q1,and a terminal disc Q2 connected to or formed integral with one terminallead L2 for the condenser is placed over the insulating disc Q1 whichlies over the severed end of the core or mandrel L. The aperture in thebase of the thimble Q through which the terminal lead L2 extends isslightly chamfered and soldered at Q3, to the lead L2 so that this iselectrically connected to the thimble Q whose base is completely sealedby the soldered joint Q3. The other, or open, end of the thimble Q isspun over into a bead Q4 which bears against a sealing washer Q5 ofmoisture-resistin material such, for example, as synthetic rubber or thelike, thereby sealing the end of the thimble Q from which the projectingend of the wire core or mandrel L extends through a central aperture inthe rubber washer Q5. The terminal leads L, La are thus againsubstantially coaxial with the rolled unit and thimble Q whose interioris again completely sealed against moisture. With this construction therolled unit may be treated with impregnant before soldering the terminalthimble Q along the slot Q1, the impregnant finding ingress through thesaid slot. The complete condenser is thereupon moulded into a housing Q8of Bakelite or other mouldable insulating material.

Instead of employing a conducting pot-like thimble, a conducting sleeveR (Figure 15) open at both ends may be used, the ends of the sleeve Rbeing sealed by spinning the annular edges R1 thereof over sealingwashers R: as described above. The wire core terminal L then extendsthrough one sealing washer R: whilst the sleeve R is provided at itsother end with a terminal tag Rs or cap to which the second condenserterminal lead Le is connected by soldering. Impregnation having beeneffected (before the sealing washers R: are applied) the sealedcondenser unit is moulded into the insulating casing R4 as abovedescribed.

Figure 16 shows an arrangement in which the wire core upon which theflexible foils and paper strips are wound comprises a plurality of wiresL4, L5, the first flexible electrode element M (Figure 12) beingattached to the core by insertion between the wires L4, L5 in the mannerdescribed with respect to the insulating core of Figures 3 to 6. Thisobviates the necessity for soldering the end of the first electrodeelement M to the core.

- In Figure 16 the second terminal lead Le may be connected to themetallised sleeve or pot within the insulating housing In after themanner described with reference to Figure 15, suitable sealing washersR2 being provided so that the rolled unit is again sealed against accessof moisture before the housing L1 is moulded thereon.

In the modification shown in Figure 17, the core is constituted by a isingle wire S to which the first foil is soldered. T1 from one end ofthe rolled unit and is soldered at T2 to a terminal disc T3 and to ametallised ceramic tube V, an insulating disc S1 being placed over thesevered end of the core S to insulate this from the foil T1. Thus,whilst one foil lies wholly within the confines of the paper spacers Wthe other foil projects from one end of the rolled unit to form one ofthe terminal connections. If desired, the ceramic tube V may be replacedby a metal tube to which the terminal disc T3 at one end, and theceramic bush at the other end, are soldered, the whole bein moulded intoBakelite or other mouldable plastic material as already described.

What I claim as my invention and desire to secure by Letters Patent is:

1. An electrical condenser comprising a core formed of at least onethread of insulating material, a plurality of interleaved flexibleconducting and insulating elements wound spirally on said core to form arolled unit, the conducting elements projecting from the confines of theinsulating elements at opposite ends of the rolled unit respectively soas to form terminal connections, an insulating tube embracing the rolledunit, said tube being metallised adjacent to the said terminalconnections, and terminal leads soldered to the terminal connections andto the metallised parts of the tube so as to seal the rolled unit withinthe tube.

2. An electrical condenser comprising a core formed of at least onethread of insulating material, a plurality of interleaved flexibleconducting and insulating elements wound spirally on said core to form arolled unit, the conducting elements projecting from the confines of theinsulating elements at opposite ends of the rolled unit respectively soas to form terminal connections, an insulating tube embracingthe rolledunit, said tube being metallised adjacent to the said terminalconnections, terminal leads soldered he second foil projects at 7 aboutthe rolled unit and insulating tube, the terminal leads extendingthrough said housing.

3. An electrical condenser comprising a core formed or a plurality ofthreads of insulating material, a plurality of interleaved conductingelectrode and insulating spacing strips wound spirally upon said core toform a rolled condenser unit, the first fiexible strip being insertedbetween the threads of said core and successive flexible strips beingwound in between said core and said first strip with the conductingstrips of oppq ite polarity projecting from opposite ends of the rolledunit to form terminal connections, an insulating tube embracing saidunit,"said tube having metal-'- lized portions adjacent to said terminalconnections, and terminal leads soldered to said termi-- nal connectionsand said metallized portions, whereby to seal said unit within saidtube.

4. An electrical condenser comprising a core formed of a plurality ofthreads of insulating material and a plurality of interleaved conducting and insulating strips, one of said strips having an end insertedbetween the threads of said core and the remaining stripsbeingsuccessively inserted in longitudinally staggered relation between saidfirst mentioned strip and said core and wound therewith into arolled'condenser unit,

5. An electrical condenser comprising a core formed of a plurality ofrelatively thin threads of insulating material, a plurality ofinterleaved conducting and insulating strips, one of said strips havingan end inserted between the threads of said core and the remainingstrips being successively inserted in longitudinally staggered relationbetween said first mentioned strip and said core and wound therewithinto 9. rolled condenser unit, the conducting strips projecting beyondthe insulating strips at the opposite ends of said unit to form terminalconnections, an insulating tube enclosing said unit in snug fittingrelation, and terminal elements in electrical contact with said terminalconnections and secured to the ends of said tube.

6. An electrical condenser comprising a core formed of a pairlofjuxtaposed threads of insulating material, a pair of conducting stripsinterleaved with insulating strips, one Of said strips having an endinserted between the threads of said core and the ends of the remainingstrips being progressively inserted in longitudinally 5 staggeredrelation between said first mentioned a plurality oi. interleavedconducting and insulating strips, one or said strips having an endinserted between the threads 0! said core and the remaining strips beingprogressively inserted in longitudinally staggered relation between saidfirst mentioned strip and said core and wound therewith into a rollercondenser unit.

8. In a condenser as claimed in claim 7, wherein the conducting stripsproject beyond the confines or the insulating strips at opposite ends ofsaid unit to form terminal connections, an insulating tube enclosingsaid unit in snug fitting relation, and conducting terminal members inelectric contact with said terminal connections and hermetically securedto the ends of said tube.

9. An electrical condenser comprising a core formed 01 a plurality ofmonofil threads of plastic insulating material, a plurality ofinterleaved conducting strips and insulating strips, one 01' said stripshaving an end inserted between the threads of said core and the ends ofthe remaining strips being progressively inserted in longitudinallystaggered relation between said first I mentioned strip'and said coreand wound therewith into 9, rolled condenser unit.

' PHILIP RAY CQUBSEY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 728,780 Splitdori May 19, 1903850,166 Lamphier Apr. 16, 1907 1,303,325 James May 13, 1919 1,573,853OLeary Feb. 23, 1926 1,744,616 Cunningham Jan. 21, 1930 1,960,944Knudsen May 29, 1934 FOREIGN PATENTS Number Country Date 452,030 GreatBritain Aug. 17, 1936 521,604 Great'Britain May 27, 1940 541,096 GreatBritain Nov. 12, 1941

